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PathSumII.java

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import java.util.ArrayList;

/**

* Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum.

*

* For example:

* Given the below binary tree and sum = 22,

* 5

* / \

* 4 8

* / / \

* 11 13 4

* / \ / \

* 7 2 5 1

* return

* [

* [5,4,11,2],

* [5,8,4,5]

* ]

*/

public class PathSumII {

public ArrayList<ArrayList<Integer>> pathSum(TreeNode root, int sum) {

ArrayList<ArrayList<Integer>> result = new ArrayList<ArrayList<Integer>>();

if (root != null) {

ArrayList<Integer> path = new ArrayList<Integer>();

findPathSum(root, sum, result, path);

}

return result;

}

public void findPathSum(TreeNode root, int sum,

ArrayList<ArrayList<Integer>> result, ArrayList<Integer> path) {

if (root == null)

return;

if (root.left == null && root.right == null && root.val == sum) {

ArrayList<Integer> clone = new ArrayList<Integer>(path);

clone.add(root.val);

result.add(clone);

} else {

path.add(root.val);

if (root.left != null) {

findPathSum(root.left, sum - root.val, result, path);

}

if (root.right != null) {

findPathSum(root.right, sum - root.val, result, path);

}

path.remove(path.size() - 1);

}

}

}